For the ease Semperfli have already removed the inner cord so that you can get straight on with tying without having to do anything fiddley. The Mylar pipe gives a stunning fish scale effect for Salmon, Trout and Saltwater flies.
With the crisscross structure of the Mylar strands in the manufacturing process this provides a glitter effect and when used as a body provides staggering attractive properties to predators.
Also you can tease the piping end loose and use as a tail.